Some surfaces of parts formed by additive manufacturing systems are often not smooth and the surface roughness affects visual properties of the part such as its translucency, color, gloss, and the like. For example, a rough surface can make clear parts appear opaque, colors can be less vivid, and surface finish can be flat or matte. Typical three-dimensional object (3D) printing processes produce widely varying surface roughness in a single object. For example, a lack of registration between the movement of material ejectors and the platen on which the object is formed can result in small misalignments between the start and end of each layer. The printing process produces parts with vertical surfaces that are significantly rougher than the horizontal surfaces of the object because the ends of the layers do not align with one another. Thus, a part made with clear material drops from ejectors has vertical surfaces that appear opaque, while the horizontal surfaces appear clear. Other surfaces of the same object are within a range of translucencies between clear and opaque. Non-additive manufacturing processes, such as injection molding, are capable of producing parts that are clear with high gloss because the melted material conforms to the smooth polished surfaces of the mold. Thus, the vertical walls of the part are formed as smoothly as the horizontal surfaces of the part.
Currently, additive manufactured parts can be treated to give them a more uniform or enhanced appearance. Conventional subtractive finishing techniques, such as sanding, polishing, and buffing, are often used, however, these methods are time consuming, difficult to perform on complex object geometries, may damage small features, and remove thin color layers. Coatings are also used, such as glycerol dips or varnish, to enhance surface gloss and color vibrancy, but they often require subtractive finishing techniques, such as polishing or buffing, to prepare the surfaces for the coatings, can have lengthy processing or drying times, and can leave the part greasy to the touch. Additionally, the coatings can later detach or peel from the surfaces or they do not match the colors of images at or near the surfaces. Thus, a system that restores uneven surfaces of additive manufactured objects without the issues raised by subtractive finishing techniques or coatings would be desirable.